Hello. As default whenever I have created a document I have used XHTML 1.0 Transitional. There is nom reason for this I just suppose it was set as my default and I stuck with it cus I knew it worked for me. I have been wondering if I am using the best doc type for my needs but after reading several other forums on what doc types people prefer however It all seems to end up on personal opinion.
What I was hoping was for someone to please explain the differences between the document types so I can choose which are best for each individual site I create. also the difference between transitional & strict and what they mean would be appreciate. Im not looking for what people prefer to use but what they actually mean. Thank you.

This may help sh00ta,
http://www.w3.org/QA/2002/04/valid-dtd-list.html
or you can google it

I am by no means an expert on the matter but here is my take DocTypes (DTD).

A DocType instructs the browser on how to properly render the document. Your choice of DTD is based on what data is presented and how you wish to present the data. If no DocType is defined the browser will render the page in quirks mode instead of a defined standards mode. The result is how the content is displayed.

HTML = Legacy standards.
XHTML = Current standards of separating content from structure.
Other DTDs = for presenting data really not applicable to most people.

Strict DocTypes adhere to the current standard.
Transitional DocTypes are more flexible, allowing developers time to transition to the new standard.

Check out this article. http://24ways.org/2005/transitional-vs-strict-markup

Make sure you follow the link "Ten questions for Tommy Olsson" in that article. It's very informative.